A multi-node computer system typically contains a plurality of central processing units (CPU) node, a plurality of interconnects, and a plurality of input output (IO) nodes. Each IO node is coupled to multiple IO devices, which may be conventional peripheral devices, such as peripheral component interconnect (PCI), small computer system interface (SCSI) type devices. Such multi-node computer system may perform complex computing tasks such as interacting simultaneously with a large number of IO devices.
In a multi-node computer system, some or all of the IO devices may be memory-mapped IO (MMIO) devices. The memory-mapped IO devices are connected to address and data lines within the IO nodes, and the CPU nodes in a manner similar to the connection of memory devices. Whenever the IO nodes, or the CPU nodes read or write the addresses associated with the IO devices, the IO nodes or the CPU nodes can transfer data to or from the IO devices. One of the advantages of such memory-mapped IO devices is that processors in the CPU nodes or the interconnect can use any single instruction that accesses their memory spaces to operate upon data that are transmitted at IO device ports rather than first moving the data into processors, manipulating the data and then writing the data back to the IO device port. By doing so, memory-mapped IO devices typically reduce computation burdens on the processors.
To support these memory-mapped IO devices, components in the multi-node computer system, including the CPU nodes and the IO nodes, need to allocate large amount of physical address space in their memory units. In a conventional multi-node computer system, the interconnect has only a fixed number of MMIO range registers to specify the range of address spaces that are allocated for memory-mapped IO devices coupled to a given IO node. Such interconnect registers are typically “base” and “size” types of registers, which requires a base and size declaration for each CPU node and IO node coupled to the interconnect. If there are n nodes in the computer system, it will require n Base registers and n Size registers. The conventional “base” and “size” type registers thus consume substantial resources.
Moreover, the conventional “base” and “size” type registers fail to provide scalability for memory-mapping in a multi-node computer system. When the IO nodes connect to a large number of IO devices, the MMIO address space requirement for the multi-node computer system can be an arbitrarily large number. It would be very inefficient for a programmer to configure every MMIO range register to specify the base and the size in the interconnect for each IO device.
Therefore, it is desirable to provide an efficient and scalable method and system to dynamically support MMIO devices in an interconnect-based multi-node computer system.